Patent GB-813506-A (GB)
Title: Improvements in or relating to combustible gas production
Inventor: GRISENTHWAITE ARTHUR TURNER
Filed: 1955-07-18
Abstract: 813,506. Production of combustible gas. POWER-GAS CORPORATION Ltd. July 18, 1955, No. 20683/55. Class 55 (2). [Also in Group XIII] In a process for the production of combustible gas by hydrolytic cracking of hydrocarbons in the presence of steam a moving mass of catalyst pebbles is first heated in a heating zone and heated catalyst pebbles are continuously passed to a reaction zone into which a vaporous mixture of hydrocarbons and steam is introduced to react therein in contact with and heated by the catalyst pebbles to produce combustible gas, catalyst pebbles being continuously withdrawn from the reaction zone and returned to the heating zone and the steam being preheated by contact with the catalyst pebbles before it is mixed with the hydrocarbons and introduced into the reaction zone. The catalyst pebbles are made from material containing nickel, or lime and bauxite, or magnesium oxide and bauxite or lime and magnesium oxide so that they have a high degree of refractoriness and are preferably in the form of balls of ¢ inch diameter. The hydrocarbons which may be used in the process may be natural gas, refinery gas or bottled propane and butane, light and intermediate hydrocarbons such as gasoline, kerosene and naphthas, or heavy hydrocarbons such as fuel oils, or crude petroleum. The apparatus for carrying out the process shown in Fig. 1 comprises a heating zone 3, a reaction zone 2 and a steam superheating zone 1 ; the catalyst pebbles descend each zone in turn and are withdrawn at the base of zone 1 by an extraction device 11, being returned to the heating zone 3 by an elevator 12. Preheated air is supplied by conduit 31 to reheat the catalyst pebbles by combustion of the carbon deposited on the pebbles. Supplementary heating may, if necessary, be supplied by combusting a fuel in a chamber 35, the hot combustion gases being admitted to the zone 3 along with the preheated air. The air for the heating zone 3 is preheated in a heat exchanger comprising two zones 51 and 50 through which refractory pebbles are circulated, the pebbles being heated in zone 51 by contact with the hot combustible gases from reaction zone 2 and used in zone 50 to preheat air admitted at 63; preheated air leaves the zone 50 by conduit 34 and an elevator 60 returns the refractory pebbles from zone 50 to zone 51. Steam admitted by line 14 at the base of the steam preheating zone 1 gathers in the space 42 and e.g. a petroleum oil is sprayed from pipe 21 so that it is volatilized by the catalyst pebbles and mixes with the superheated steam, the mixture passing upwardly into the reaction zone 2. Combustible gas is withdrawn through outlet 25 and passes off through conduit 27, the heat exchanger zone 51 and an outlet 74. The gas produced has a calorific value around or below 500 B.Th.U's and in an example operating temperatures are: catalyst pebbles enter the reaction zone 2 at 1100‹ C.: steam is superheated to 800‹ C. in zone 1 and air is preheated in zone 50 to 400‹ C. In a modified apparatus an additional chamber in which steam is more highly superheated is provided intermediate the heating zone 3 and the reaction zone 2. Also a small additional zone is provided between the reaction zone 2 and the steam superheating zone 1, the hydrocarbon to be gasefied being introduced into this additional zone. The catalyst pebbles are elevated from zone 1 to zone 3 by pneumatic means and sensible heat in the gases leaving the pneumatic elevator and the heating zone may be used in preheating hydrocarbon oil and/or in a waste heat boiler.